This invention relates to a suction device for an engine and more particularly to an improved engine induction system.
A common form of induction system for an internal combustion engine includes a first intake passage that extends from the intake port of the engine to a plenum chamber and a second passage that extends from the plenum chamber and which forms an atmospheric air inlet. Frequently, the plenum chamber is the body of an air cleaner for filtering foreign objects from the inducted air. It has been found that this type of system can result in poor running at mid ranges. This poor running results in a torque curve that is not as flat as desirable and also in reduced mid range power. It has been found that these conditions are the result of incomplete combustion in the combustion chamber.
The inventors have discovered that the reason for this is that the sequential opening and closing of the intake port, be it a ported construction as in a two-cycle engine or a valved construction as in a four-cycle engine, causes negative pressure pulses to propagate through the induction system to the air inlet which, at certain engine speeds, synchronize with the characteristic frequency of the induction system and cause resonations. These resonations generate large pressure variations in the plenum chamber and substantially decrease the volumetric efficiency of the engine. In addition to diminishing the volumetric efficiency of the engine, these pulsations in the induction system cause irregularities in the mixture strength delivered either by the carburetor or the fuel injection system and, accordingly, the emissions of unwanted exhaust gas constituents is also increased.
It is, therefore, a principal object of this invention to provide an improved induction system for an internal induction engine.
It is a further object of this invention to provide an induction system for an internal combustion engine in which pulsations in the inlet system are dampened.
It is a further object of this invention to provide an improved induction system for an engine embodying a plenum chamber wherein pulsations in the plenum chamber are substantially reduced under all running conditions.